Method of and apparatus for testing magnetizable objects



June 26, 1923. M5591@ I C. W. BURRCWS METHOD OF AND APIAARATUS FORTESTING MAGNETIZABLE OBJECTS Filed July 25 1917 5 sheets-sheet 2 Jl'meZ,1923. I

y C. W. BURROWS METHOD or AND APPARATUS Fox TESTI-NG -MAGNETIZABLEOBJECTS Filed July 25 1917 5 Sheets-Sheet 5 Jm ze, 1923. 4 1.459,9?0

c. w. BuRRows METHOD 0F AND APPARATUS FOR- TESTING MAGNETIZABLB OBJECTSFild July 25 1917 -5 Sheets-Sheet 4 4 1.459.970 c. w; BuRRows METHOD 0FAND APPARATUS FOR TESTING MAGNETIZABLE OBJECTS Filed July 25 1917 ssheets-sheet 5 lavendel Patented June 2e, 1923?.

" STATES CHARLES w. BU-nnows, or WASHINGTON, DISTRICT or COLUMBIA,AssIGNon OF ONE- FOUaTn To RUDOLPH I. wIG, or WASHINGTON, DISTRICT orCOLUMBIA,

'ITETIIOD or'V Nn ArrAnaTUs roza TESTING MAGNETIZABLE OBJECTS.

p Application area July 25,

The object of this invention is -to enable vthe relative hardness orstructural quality of small objects made o f magnetizable mate- L rialsuch as iron or steel to be determined by what I term magnetic analysis.'This magnetic analysis consists in the determination of the magneticcharacteristics, or a number of ma etic characteristics loi? a ivenma-gnetiza lebody, such as a steel ob- ]ect, and from and by thesedetermining the physical'properties of such body or object.

The science of magnetic analysis consists of the systematic correlationoi the magnetic and other properties of materials and of the applicationof the laws and principles which underlie the interrelations of such prorties, particularly the 4interrelations of t e ma etic and mechanicalproperties of steel.V t is based upon the fundamental fact ofobservation that there is one, and only one, setof mechanicalcharacteristics corresponding to a given set of'magneticcharacteristics, and conversely there is one,

and only one, 'set of magnetic characteristics corresponding to a givenset of mechanical characteristics. p The vparticular object of thepresent invention is to enable the physical qualities or e0 relativehardness of the small magnetizable.

bodies or objects to be determined rapidly,

and with practical commercialr accuracy,

without having to injurein any way the Object being tested, and toprovide a simple apparatus by which each andeveryarticlev may be testedif desired, to determine whether or not it-is above or below apredetermined standard; and tondo away with the expensive and uncertaintesting methods heretofore employed, such as subjectingthe article toabrasion, mechanical stresses, or chemical treatment, or to 'microscopicanalysis. It is well known that apparently similar isfactoryAinf'g'eneral,

1917.- Serial No. 182,716.

or duplicate metallic Objects will vary in physical' and magneticproperties-f. i. stee objects made from the same ingot, and treated asnearly as possible by the same methods in their manufacture, will varyin their rela- 4 tive physical qualities, such as hardness and strength,according to variation in the temperatures, or differences of time ofheating or cooling, or different mechanical stresses, to which they mayhave been subjected in their making; and they may also differ even ifsubjected as far as'humanly possible to exactly the same conditions oftreatment in every step of their process of manufacture; but I havediscovered a method and means by which each such ob`ect may be readilytested by magnetic analysis and the differences therein immediatelydiscerned.'

The ideal test of a finished product is one which permits theexamination of each individual -object and does not assume that vthecharacteristics of ninetyenine 'objects are identical with those of thehundredth onel which may happen to be picked out for test. Magneticanalysis is adapted to such individual testing and not only permits -theelimination of defective objects but also permits the grading of are notall of the' same .degree'of perfection, and will enable manufacturers toproduce objects of a uniformity hitherto unknown-and to guarantee suchuniformity with, surety.

To more readily enable others'to fully understand the inventlon and itspracticability,

objects which, while satas 'ball races or rings commonly employed 'inball bearings, which rings are made o' highly tempered steel and must becapable of withstanding great pressure safely.

The present usual methods of testing such rings is byfli'les forhardness, and by shock for brittleness; that is, after the rings havebeen formed; each ring is subjected to a file test byv hand, and the tobe skilled enough to termine by the efo rator is su osed dpe@ Pp at..

fect of the file upon the ringwhether or not it is suitably tempered andof suicient hardness. `Ifthe ring passes this test, it is" I droppedfrom a predetermined height onto a non-yielding'surface, and if itcracks is thrown aside.-

ioa The l'e test uncertain, as it certained as hereinafter explained.

depends upon the feel of the operator and the pressure and sharpness'oi''the file; and

the droppingytest 'is uncertain because some f the shock but not ringswill be flawed by ft f e un i I vor service.

noticeably cracked, whi

My invention avoids any mechanical stress or strainand obviates `alluncertainty rei, garding the physical qualities of the rings;

they can by, my invention be tested at any stage of their process ofmanufacture, and also when finished; the test can be rapidly made bypersons of ordinaryintelligence greater certainty of results than ispossibly obtainable by mechanical, chemical or microscopic methods.

I test such rings or likeobjects by subjecting them 'to magneticanalysis in a novel lmanner and by anovel apparatus which is based uponthe fundamental fact that there is a definite relation betweenthemagnetic y and other physical properties of steel, which fact has beenso thoroughly established that the successful application4 of magneticanalysis for 'commercially testing steel rings or like small objects inthe manner hereinafter stated is assured.

In carrying out the present invention the ring, or object to be tested,is subjected to the action of a relatively rotated magnetic field 'offorce, which ield may be produced in various ways (asby rotating themagnet or magnets around the object to be tested, or rotating theobjectA within thel magnetic field,

. or establishing a rotating magnetic field by means of a polyphasecurrent `directed Ythrough an annularseries of magnets, or by properlycommutating a direct current successively vthrough a series of properlyarranged magnets, or by producing a split phase rotating j phasecurrent) so that the obj ect being tested 1s subjected to a rotativemagnetic flux `and means are r'ovided whereby the amount of the magneticstress on such object or'torclue ma be communicated to a suitable visualor' audible indicator, and if desired to a suitable recorders; so. thatwhen thel object is subjected to the action of such field, the operatorcan readily observe from the indicator the stresser torque exerted uponsuchob- .Assumin for instance, that a visual indicator is .use theoperator can,l by noting its deflection, within certain limits,determine at once whether the object possesses the predeterminedrequisite physical qua-lities and is therefore to be accepted, orWhether it lacks such qualities and is to be'rejccted.

The definite standard by which the' aci ceptability or rejection of theobject to be treated is determined is to be previouslyv as- I will firstdescribe a simple laboratory apparatus for testing ball races andlikeobjects and then a practicalcommercial apparatus for testlng suchobjects. Y

lin a sleeve Referring to the accompanying `drawings,f

Figure 1 is an elevation of `oneapparatus embodying the invention, andFigure Qris an enlargedsectlonal View of the. upper portion of suchapparatus.

, F lgure 3 is aside elevation' ofv an appara-l Atus particularlydesignedvfor testing ballthe top plate and pole-pieces being removed.

Figure 6 is an underneath view of 'the top plate and attachedpole-pieces.l

Figure 7 is a detail sectional` View on the line Tp-7, Fig. 5.

Figure 8 is an enlarged detail view of. the ob 'ect-holder. j

`igure 9 'is a detail plan view of the object holding devices detached.

Figure l() is a side view thereof,nand F igure 1l an edge View of thevobject holding devices.l

Figures 12 and 13 are detail sectional views.

Referring to Figs. 1 and 2, a designates a holder for' the object to beteste-d, which holder may be suspended by a torsion wire c froml anysuitable overhead support or bracket c. The holder is preferably guideda which in turn is adjustably mounted in a guide a2 by means of tapscrews a3, and this supportediby any suitable means, as by a bracket a*attached to the wall below bracket c. The holder a carries an indicatord which is adapted to swing past a graduatedV guide a2 may be fixedlywhich may be A porting frame z' beneath the holder,- and :carries a gearj meshing witha pinion lc on the shaft Z of the armature of an electricmotor m. All the aforesaid parts may be of any suitable or preferredconstruction, and are conventionally illustrated in the drawing, butthose skilled in theart. will be readily able to understand, constructand use the same. e f 1 When the magnet f--g is rotated its poles movearound the object b, and create a .ro-

tating magnetic field, and the magnetic flux or induction producedthereby in the object b will tend to cause said object to turn with themagnet according to the physical nature ,of the object and theresistanceof the 'torsion wire c or other suitable spring means opposing therotation yof theobject. The

llli

or torque on tha object is readily deter-l mined by noting the movementof the pointer lon scale e either during or after the periodofdeliection or rotation but before the magnetic torque or stress hasdropped or ceased.

The magnetic stress or torque exerted by the rotating magnet upon theobject con'- tnues an appreciable time after the rotation stops, andeven a momentary rotation of the field is enough to cause a' deflectionof the object, if relatively small. The effect of whirling or rotationof the magnetic field upon a standard object b having been previouslydetermined and noted upon the scale e, thesimilart' of 'another likeobject to the standard o ject can be at once deter-A mined bysubstituting the same ff r the standard ,object and observing whether.or not the pointer d is defiected to the same point on the scale e thatit assumed when the standard object b was in positionin the machine.

If for instance the parts had been so ad- 'justed that the pointer dwould stand at zero when the standard object is in the machine under theactiony of the rotating field, it follows that if a like object, exactlycorresponding with the standard object, is sub-- jected to the samerotative field inthe samemanner, the pointer d will move to the samepoint on the scale, and that any variation ofthe position assumed by thepointer above or below such point. would show th'atthere lwas-'amagnetic diEerence between the objects being tested and the standardobject, and a corresponding actual physical .difference between theobject being standard object. If in suoli test the pointer d stops belowsuch' standard point-one kind of physical defect-as too great softnesswill be indicated; if the pointer d passes above such standard pointanother'physical defect-as excess hardness or brittleness will beindicated.

APractically the same effects could be produced and the same method oftesting applied -if instead of rotating the magnet or magnetic fieldaround the object, the object was rotated in the magnetic field, andthis of the invention but for most purposes lI preer to rotate themagent or magnetic The simple form of apparatus shown in Figs. 1 and 2could be used'for testing various objects, but was more particularlydesigned for laboratory. use.

A commercial form of the apparatus is' shown in Figures 3, to 13. Thisincludes a 'three-phase electro-magnet, the core' portions .1, 1 and 1",of vwhich are preferably made of laminated plates of magnetic materialof high permeability and low core loss and tested and the matelyU-shapedplates; each plate forms part of two adjacent core pieces andthe connecting yoke, and the plates are arranged as shown in Fig. 5, sothat there will Y be a uniform and` continuous metal conduit for themagnetic lines of force at the base of the apparatus between the severalcores 1, 1*3L and l". These laminated plates may be mounted on a basemember 2, which vmay be made ofnon-magnetic materialof any suitableconstruction and is provided with pairs of radially disposed anges 2a toand between which vthe yokes are fastened by means of bolts 2b asindicated in the drawings (Fig. 13). .l

The upper ends of the cores 1a are connected to and by a plate 3. whichshould be made of non-magnetic material and is provided with openings 3for the upper ends of the cores, and may be supported on and fastened tothe upper ends of posts 2'rising from base 2 intermediate the poles asshown. The binding posts for the electrical connections to and betweenthe several coils-1c are arranged on the base 2 as shown at 1 and 1 sothat the coils of several cores may be properly connected in sequence.

The upper magnetic pole pieces 1*,1t and i e shown are made of laminatedplates like the cores andattached to a removable top plate or casting 4which is provided lwith pairs of parallel radially disposed iianges .4to and between which the pole pieces are secured by means of bolts 4" asindicated in the drawin s.` late 4 is provided vwithdepending studs 4corresponding in position to posts 2c and adapted to overlie the same.And the plate 4 may be detachably secured to posts 2 bymeans of bolts 4passing through openings in studs 4 and engaging threaded sockets inposts 2c as shown. When plate 4 is in position over the plate 3 theundersides of the poles 1, 1f, 1g have 'a close metallic contact ywiththe upper ends of the cores 1, 1, 1*', and yform magnetic continuationso2 the converse action I consider within the scope cores; and a magneticfield will be created adjacent to and yintermediate the ends of g thesepoles 1, 1, 1g when parts are properly assembled and the magnet isenergized.

The base`2 is preferably, and plates 3 and 4 should be, made ofnon-magnetic material so that they will not disturb the lines of force,and the most intense field of force will be established between the inner ends of the poles 1, 1', 1.

Arranged between the magnets coils and below the plate 3 is aframe 5(Figs. 7-10 and A11) which may be supported andguided in brackets 3,301'1 the plate 3, and is prefy frame has a' stud 5 on its lower endwhich usA is adapted `to be engaged with a socket 2 in' a stud-on `basemember 2, see Fig. `7, to hold the -frame securely and verticallyadjustably in place.

In frame vis a rotatable lspindle 5, which -may be mounted on'pi'votbearings as shown,

or other suitable bearings., so that it will turn without perceptiblefriction. To the spindle 5a is connected one end of a spring 6, (Figsrand 1l) the other end of which is connected to a relatively fixed'point,and its tension may be regulated in any suitable manner. As shown theouter end of the springis attached to an annulus 6a guided in brackets6b on the sides of the frame 5; and this a'nnulus has internal teethlengaged by a small pinion 6c'on a key-shaft 6l (Figs. 7' and 9)journaled in a bracket 6e attached to the frame 5 5 and by turning key6g the annulus can be turned to regulate the tension of the spring 6 andthe annulus can be locked when adjusted by any suitable means.

As shown 'shaft 5a carries a yoke 5bon its upper end, which embraces andrises above.

the top bar of the frame 5 and carries an object support 5d, (Figs. 'i'and 8) which may be detachably attached thereto; said support being.made of non-magnetic materiaL-and has' in the example' shownv anyannular portion 5e over whicha ball race R to be tested can beremovably fitted; such ball race being readily replaceable or removablefrom the support 5d. An indicating finger 5F is attached to yoke 5,1 andis bent so that-its outer end moves past a graduated scale 7 which therace and the' resistance of the spring may be suitably supported uponthe plate 3,.

as indicated in the drawings. The scale 7 lies beneath a sight opening4P in plate 4, which opening, may be covered by a glass 4' as shown. A

The-ball-race to be tested can be supported closely adjacent to andbetween the .inner ends of the poles 1, 1f, l", and'if'the magnets wererotated, such ball race would be subjected tothe action of a rotativemagnetic field. In the construction shown, however, instead of rotatingthe magnet, Vthe coils are energized' successively by the oomponents ofathree-phase current, or by a suitably commutated direct current, so asto create a rotative orpwhirling magnetic field of force between thepoles. This rotative magnetic ield'will establish a magneticiiuxo'r-stress in the ball race or object R which will tend to cause thisrace to turn with the" rotating field, and amount of the torque and .theextent to which the race will be turned will .depend upon the physical'properties of 6 to rotatory displacement of the spindle 5*-which carriestherace or object to be tted.

The specific constructions of parts shown ,are not :essentials ,of thepresent; inventionV eIlCeS.

y removed and and maybe varied by skilled mechanics to .suit theparticular objects to be tested.

I will describe the method and use of the apparatus shown in. Figs. 3 tollin` testing ball-races for ball bearmgs.

It is known that two 'pieces of steel or iron may differ in any one or anumber of particulars and'it iS also known that each physical differencehas an eiiect upon the magnetic properties of such piece of steel, thatis, any two pieces of steel or objects which dif- -fer in certainphysical particulars will 1ikewise show corresponding magnetic differ-Assuming that the desired physical properties of a race havebeendetermined and such a race placed on the support 5d and the partsadjusted so that when the current is on and the magnets energized theindicator 5 will stand at the 0 point on the scale for instance; vitfollows that 'if such standard race is removed and another race isplaced on the support which exactlyl conforms to the standard racein-physical properties the pointer will move to the point 0 when the'magnets are energized, `a standard current being always used. If a racevaries in any physical particular from 'the standard race, that factwill be shown by a corresponding variation in the amount-ofy deflectionvof the support 5d and indicator 5c, and if this variation comes aboveor belowcertain predetermined limits, such race must be rejected.

In this manner and)by this method and apparatus an operator can veryrapidly test any numberV of races or objectsf designedto be of thesamequality and size, and can*l very brittleand liable to break under suddenshock, can bedetected and rejected, and

they can be kept together forproper treatment to reduce their hardness.0n the other hand, if a race be too soft the indicator willynot be movedto the proper limit and such excessively soft races can bedetected,placed togetherl for 'further Vertles have been studied. With increasinvcarbon content there is an increase in har toughness. Magnetica y a nincrease in carbon content is accompanied by an increase sacl Many ofthe changes that are brought l -nesrs .and tensile stren h and adecreasein in coercive force and hysteresis, and a decrease inpermeability.

Mechanical operations also bring about corresponding changes in both themechaniv cal and the Amagnetic properties of steel.

The cold drawing of a carbon steel increases its tensilestrength andsimultaneously in creases its 'coercive force and hysteresis. Colddrawing also decreases the magnetic permeabilit That varlations arecaused by differences in heat treatment upon thel properties of steel isknown-f. i. a one per cent carbon steel uenched at a temperature aboveits critica point has a greater tensile strength than the same materialin the annealed condition. Its hardness is also increased while culatedthat `when the object to be tested is laced thereupon and subjected tothe actlon of a rotating magnetic field, or rotated within the magneticfield the difierences in physicalproperties will be detected as stated.

Concisely stated-the at present preferred practical ap aratus consistsof a rotatable member an movement of the rotatable member, whetherobject or magnet, is constrained by means whose resistance becomes afactor in determining the physical natureof the object.

An object such as a pipe or rod may be rotated on its longitudinal axisbetweenthe poles of the magnet .and simultaneously' moved longitudinallybetween the poles, or the magnet moved longitudinally of the object, andin this way the physical properties of each cross section of such objectcan be tested, by the method hereinabove explained. In this way rods,tubes, rails, bars,

i etc., can be tested to detect inhomogeneities tate the object such asa blow holes, strains, flaws, etc.

As the ower necessary to rotate the magnetic fiel or turn the magnet, isgreater when the object is ini/place than when it is not; and likewisethe power necessary to roma et is exci than when it isv notexc1ted,-therefore` the power necessary to drive the rotating part(whether magnet, field or object), becomes a measure of the hysteresisofthe object and vtherefore of its mechanical hardness.

While in b oth the laboratory and the coma stationary member. The.

ing a rotating or whirlin itsmgreater when the electro-l mercialapparatus the object to be tested is placed on a substantially fixedsupport and the magnetic field rotates around the vobject it would bepractical to rotate the objectwithin a stationary field in which casethe'effect would be the same with the field rotating relg atively to theobject. In other words substantiall the samemagnetic effect would beproduce in the object by whirling the object in a ma netic field as bywhirling the magnetic fie d around the object as in each case thereoccur the same changes of magnetic flux within the object, the samemagnetic stresses are producedV in .the object, and there is the sameinteraction between the fixed and rotating parts and by measuringthedisplacement of the object or field relative toa fixed point ineither case the physical properties of the object can be determined inthe. manner hereinbefore explained. The invention therefore is notlimited to-any specific form of apparatus as the Vmethod of testing mabe emp oyed with any apparatus constructe and operated to produce arelative whirling or turning of the object and magnetic field, as andfor the purpose stated.

claim:

1. The herein described method of ascertaining thehardness, tensilestrength, homogeneity, presence of flaws and previous heat treatment, ofmagnetizablev objects, consisting in subjecting such object to theaction ofa relative rotating or whirling magnetic field, yieldinglyrestraining the relative deflection of said objects and field, anddetermining the physical properties of the object by the extent of themagnetic interaction or strength of the torque developed between the'object and the field. 2. The herein described method of ascertaining thehardness, tensile strength, homogeneity, presence of flaws and previousheat treatment of an object; consisting in producmagnetic field, placingsuch object in saidgfield, yieldingly restraining the relative rotationof said objec and field, observing the defiection of such object causedby such magnetic field in relation to a relatively fixed point, anddetermining the physical properties of the object by the extent of suchrelative' deflection.

3. The herein described method of ascertaining the hardness, tensilestrength, homogeneity, presence of'flaws, and previous heat treatment ofapproximately circular and spherical steelobjects, consistin in placingsuch objects wlthin a relative y rotating or whirling magnetic field,yieldingly restrain the relatlverotation of such object.

and fie d, observing the deflection of such ob-.

ics

ing a three-phase electromagnet the upper :so 'ing a :three-phaseelectromagnet the upper homogeneity, presence of flaws, and previousheat treatment of approximately circular und spherical steel objects,consisting in producing a rotating magnetic field, placing such obj ectin said field, restraining the relative rotation of said object andfield, observing ythe deflection of such object caused by such `magneticfield in relation to a relatively fixed point, and determining thephysical properties ofjthe object by the extent of suchV Vrelativedefiection.

5. Apparatus for testing objects, compris"-f pole pieces of saidlmagnetA being removable -and changeable, means disposed intermediate thepoles of the magnet adaptedvto carryV the object to lbe tested, andmeans for indicating the displacement of the object.V

6. Apparatusfor'testing objects compris` lmy own, I affix my signature;

pole pieces of said magnet being removable and changeable, a supportdisposed intermef7. The herein described apparatus for. testi' ingobjects, comprising a three-phase electromagnet the upper pole pieces ofsaid magnet being removableV and `changeable; aremovgable supportdisposed intermediate the up- 'per` pole pieces adaptedto carry theobject to be tested, means for yieldingly restraining the rotation ofvsaid support; and means for indicating the displacement of the object.

In testimonyl that I claim' the foregoingas CHARLES W.r BURROWS.A

